Provided by: ntp_4.2.8p4+dfsg-3ubuntu5_amd64 bug

NAME

       ntpd - Network Time Protocol (NTP) daemon

SYNOPSIS

       ntpd [ -46aAbgLmnNqx ] [ -c conffile ] [ -f driftfile ] [ -i jaildir ] [ -k keyfile ] [ -l
       logfile ] [ -p pidfile ] [ -P priority ] [ -r broadcastdelay ] [ -s statsdir ] [ -t key  ]
       [ -u user[:group] ] [ -U interface_update_interval ] [ -v variable ] [ -V variable ]

DESCRIPTION

       The ntpd program is an operating system daemon which sets and maintains the system time of
       day in synchronism with Internet standard time servers.  It is a  complete  implementation
       of  the Network Time Protocol (NTP) version 4, but also retains compatibility with version
       3, as defined by RFC-1305, and version 1 and 2,  as  defined  by  RFC-1059  and  RFC-1119,
       respectively.   ntpd  does  most computations in 64-bit floating-point arithmetic and does
       relatively clumsy 64-bit fixed-point  operations  only  when  necessary  to  preserve  the
       ultimate precision, about 232 picoseconds.  While the ultimate precision is not achievable
       with ordinary workstations and networks of today, it may be required with future gigahertz
       CPU clocks and gigabit LANs.

       The  daemon  can  operate  in  any  of  several modes, including symmetric active/passive,
       client/server broadcast/multicast and manycast.  A broadcast/multicast or manycast  client
       can  discover  remote  servers, compute server-client propagation delay correction factors
       and configure itself  automatically.   This  makes  it  possible  to  deploy  a  fleet  of
       workstations without specifying configuration details specific to the local environment.

       Ordinarily,  ntpd  reads  the  ntp.conf  configuration  file  at  startup time in order to
       determine the synchronization sources and operating modes.  It is also possible to specify
       a working, although limited configuration entirely on the command line, obviating the need
       for a configuration file.  This may be particularly appropriate when the local host is  to
       be  configured  as  a  broadcast/multicast client or manycast client, with all peers being
       determined by listening to broadcasts at run time.

       Various internal ntpd variables can be displayed and configuration options  altered  while
       the daemon is running using the ntpq and ntpd utility programs.

       When ntpd starts it looks at the value of umask, and if it is zero ntpd will set the umask
       to 0222.

OPTIONS

       -a     Require cryptographic authentication for broadcast  client,  multicast  client  and
              symmetric passive associations.  This is the default.

       -A     Do  not require cryptographic authentication for broadcast client, multicast client
              and symmetric passive associations.  This is almost never a good idea.

       -b     Enable the client to synchronize to broadcast servers.

       -c conffile
              Specify the name and path of the configuration file, default /etc/ntp.conf.

       -f driftfile
              Specify the name and path of the frequency file, default /etc/ntp.drift.   This  is
              the same operation as the driftfile driftfile configuration command.

       -g     Normally,  ntpd  exits  with  a message to the system log if the offset exceeds the
              panic threshold, which is 1000 s by default.  This option allows the time to be set
              to  any  value  without  restriction;  however,  this can happen only once.  If the
              threshold is exceeded after that, ntpd will exit with a message to the system  log.
              This option can be used with the -q and -x options.

       -i jaildir
              Chroot  the  server  to  the  directory jaildir.  This option also implies that the
              server attempts to drop root privileges at startup (otherwise,  chroot  gives  very
              little additional security).  You may need to also specify a -u option.

       -I [address | interface name]
              Open  the  network  address  given,  or all the addresses associated with the given
              interface name.  This option may appear multiple times.  This option  also  implies
              not  opening  other  addresses,  except  wildcard  and  localhost.   This option is
              deprecated.  Please consider using the configuration file interface command,  which
              is more versatile.

       -k keyfile
              Specify  the  name and path of the symmetric key file, default /etc/ntp.keys.  This
              is the same operation as the keys keyfile configuration command.

       -l logfile
              Specify the name and path of the log file.  The default is  the  system  log  file.
              This is the same operation as the logfile logfile configuration command.

       -L     Do not listen to virtual IPs.  The default is to listen.

       -n     Don't fork.

       -N     To  the  extent  permitted  by  the  operating  system, run the ntpd at the highest
              priority.

       -p pidfile
              Specify the name and path of the file used to record the ntpd process ID.  This  is
              the same operation as the pidfile pidfile configuration command.

       -P priority
              To  the  extent  permitted  by  the operating system, run the ntpd at the specified
              priority.

       -q     Exit the ntpd just after the first time the clock is  set.   This  behavior  mimics
              that  of the ntpdate program, which is to be retired.  The -g and -x options can be
              used with this option.  Note: The kernel time  discipline  is  disabled  with  this
              option.

       -r broadcastdelay
              Specify  the  default propagation delay from the broadcast/multicast server to this
              client.  This is necessary only if the delay cannot be  computed  automatically  by
              the protocol.

       -s statsdir
              Specify  the  directory path for files created by the statistics facility.  This is
              the same operation as the statsdir statsdir configuration command.

       -t key Add a key number to the trusted key list.  This option can occur more than once.

       -u user[:group]
              Specify a user, and optionally a group, to switch to.

       -U interface_update_interval
              Number of seconds to wait between interface list scans to pick up  new  and  delete
              network  interface.   Set  to  0  to  disable dynamic interface list updating.  The
              default is to scan every 5 minutes.

       -v variable, -V variable
              Add a system variable listed by default.

       -x     Normally, the time is slewed if the offset is less than the step  threshold,  which
              is  128  ms  by  default, and stepped if above the threshold.  This option sets the
              threshold to 600 s, which is well within the  accuracy  window  to  set  the  clock
              manually.   Note:  Since  the  slew  rate of typical Unix kernels is limited to 0.5
              ms/s, each second of adjustment requires an amortization interval of 2000 s.  Thus,
              an  adjustment  as much as 600 s will take almost 14 days to complete.  This option
              can be used with the -g and -q  options.   Note:  The  kernel  time  discipline  is
              disabled with this option.

       -4     Force IPv4 DNS name resolution.

       -6     Force IPv6 DNS name resolution.

FILES

       /etc/ntp.conf
              default name of the configuration file

       /etc/ntp.drift
              default name of the drift file

SEE ALSO

       ntp.conf(5), ntpdate(8)

       The  complete  documentation  can be found at /usr/share/doc/ntp-doc/html/ntpd.html in the
       package ntp-doc.